Topic Author
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Joined: Fri Jan 21, 2000 2:18 am

Airliners Taxiing

Sat Jan 22, 2000 11:18 pm

Can someone tell me what mechanism a pilot uses to steer the plane on the ground? Is there a little wheel? How do you guys do it so precisely? Whenever i try on a PC flight simulator, I drive into the terminal. Also, how do you stay so straight on the runway during the takeoff tun? Thanks.
"Sympathy is something that shouldn't be bestowed on the Yankees. Apparently it angers them." - Bob Feller

RE: Airliners Taxiing

Sat Jan 22, 2000 11:30 pm

To "steer" planes on the ground (and keep them lined up on the runway), pilots use the rudder pedals. These pedals are connected to the rudder (which is one the tailfin). In many planes, these pedals are also connected to the front landing gear, for extra manuverability. When staying lined up on the runway, pilots often use the rudders to compensate for the wind.

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RE: Airliners Taxiing

Sat Jan 22, 2000 11:34 pm

LHMark - which Flightsim are you using, it's much harder to steer using the keyboard in any of the Microsoft Flight Simulators.

Back to the topic, pilots use a tiller wheel located to their side. Some airlines have two, some only have one for the captain. This gives the maximum steering effect, causing both the nose & main gears to steer.

WentOnA777, you are partially correct. The rudder pedals are used to steer - but ONLY when on the runway, as they cannot give enough rudder authority to do tight turns. As the aircraft approaches VMCG, the nosewheel steering disconnects and the rudder pedals work on the rudder (in the case of the A340, where a limit of 4° occurs over 100kts)


CX Flyboy
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Joined: Sun Dec 26, 1999 6:10 pm

RE: Airliners Taxiing

Sat Jan 22, 2000 11:34 pm

In an airliner, pilots use a small wheel called a tiller, which is located to the side of the pilot under the side windows. This is connected through linkages down to the nosewheel. It is a lot easier to control than in something like flightsim. If you drive, you will know how accurate you can be in putting the car exactly where you want it. In a computer-based driving game it is not that easy. Airliners usually taxy at around 10-15 knots in the parking area and up to around 30 knots out on the open taxiways. At these relatively low speeds it is not hard to keep to the centerlines. When parking, you have either marshallers or auto docking systems that guide you into the exact position with precision. As you approach the stop bar in the parking bay you are only going 2-3 knots, so you don't overshoot and crash into the terminal!!

The same goes for keeping the aircraft on the centerline during takeoff...except you are going faster, although in bad conditions it can be difficult.
CX Flyboy
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Joined: Sun Dec 26, 1999 6:10 pm

RE: Airliners Taxiing

Sat Jan 22, 2000 11:46 pm

WentOnA777 could have been right if he was referring to a light aircraft, inwhich cae hydraulic power, and tillers don't come into it. Just good old mechanical cables and rudder pedals. Real flying.
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Joined: Sun Nov 21, 1999 11:44 pm

RE: Airliners Taxiing, Ask The Teacher

Sat Jan 22, 2000 11:47 pm

Hi Everybody, Buzz here. Jacob, i'll have to disagree a bit. Among other things at work i teach mechanics to taxi 727's, 737's, 757's, A320's...... things that UAL leaves at PDX overnight.
Yes, the rudder pedals are connected to the nose gear steering. Buy on a 737 you only get 7 degrees of motion. It's enough to keep you straight on the runway once you're lined up. But not enough to make the turns on the taxiway.
My favorite DC-3 has -no- connection between the rudder and tailwheel. You are expected to use a lot of rudder and the "opposite engine" to make the airplane turn. You sort of blow it around a corner: Left turn? full left rudder and power up the right engine.
On modern airliners there is a "tiller" (A320's and 747's have one on each side) near the captain's outboard knee. That gives up to 78 degrees of turn when you swing it. Yes, it's power steering.
DC-8's looked like a 6 inch diameter wheel. 737's have a 1/4th of a wheel. 757 /767 have a football shaped knob on what looks like a window-roll-down crank, and the A320's tiller looks like a horizontal ski pole grip. I can imagine you have difficulty taxiing on the PC. Better read up on what engages nose wheel steering is the only thing that comes to mind. Got hydraulics? No Hydraulics, no steering. One instructor did that to me in the DC-8 simulator a dozen years ago....... just like the movie "Airplane" with the 747 through the glass. Yes, i do check brake pressure before i make the last turn into the gate!
Buzz Fuselsausage: Line Mechanic by night, DC-3 Crew Chief by choice
Posts: 3549
Joined: Tue Oct 26, 1999 11:34 am

RE: Airliners Taxiing

Sat Jan 22, 2000 11:57 pm

Jacob is correct for light a/c.

On airliners there is a tiller by the side of each pilot, these are linked by cables to a steering control valve which controls the nosewheel position hydraulically through a couple of steering jacks. Another set of cables which go around the noseleg to feedback the nose leg position to the control valve. These cable gradually close off the hydraulics to the steering jacks as the leg reaches the desired postion.

Some airlines also have 'Rudder Fine Steering' which connects the rudder pedals to the steering system but nosewheel steering is limited to approx 7 degree's either side of neutral. The tiller steering giving you about 75 Degs either side of neutral.

On Airbus a/c the tiller is connected to the Control Valve electrically as is the Leg postion feedback.

As for actually taxiing the a/c, to taxi in a straight line the secret is to keep the taxiway centreline appearing to run up the inside of your "inboard" leg when sitting in the cockpit.

When to start a turn depends on the postion of the noseleg as compared to the cockpit - the further aft of the cockpit the leg is the later you leave the turn. Another factor is the length of the a/c, make sure you don't cut the corner and put the main gear in the grass.

On a 747 judging the turn is not to bad as the nosegear is more or less directly below you. On a DC-10 you start your turn much later. I dred to think when you start the turn on Concorde.

My experience comes from having taxied 747's, DC-10, A320's & A340's for maintenance purposes.


RE: Airliners Taxiing

Sun Jan 23, 2000 1:06 am

Sorry guys...I didn't fully read the topic and was talking about light aircraft. I have only flown (I mean flown, as in sat in the cockpit, etc..) planes twice, and they were both light GA planes (I'n only 14...LOL). The last one was a Piper Seneca 300, and that had the rudder pedals connected to the nosegear--that's what I was referring to. Sorry about the confusion...


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